1. Field of the Invention
The present invention relates to a disk brake having a disk rotor which can be braked by a brake caliper.
2. Description of the Related Art
Disk brakes which have a disk rotor which can be braked by a brake caliper are well known in the art as a brake system for a motor vehicle such as an automobile or the like. The disk rotor may be a solid disk which comprises a single circular plate or a ventilated disk which comprises two annular circular plates with a cooling air passage defined therebetween.
FIG. 7 of the accompanying drawings schematically shows a disk brake having a disk rotor in the form of a ventilated disk which is in general use. As shown in FIG. 7, when a braking force is applied from a brake caliper 2 to a ventilated disk 1, the speed of rotation of a wheel 4 which is fastened to the ventilated disk 1 by wheel bolts 3 is reduced.
The ventilated disk 1 comprises a hat 6 which accommodates a hub unit 5 supporting the wheel 4 and a disk element 7 for receiving a braking force from the brake caliper 2. The disk element 7 has first and second annular circular plates 8, 9 extending parallel to each other, with cooling fins 10 and a cooling passage 11 interposed therebetween. The second annular circular plate 9 is integrally joined to the hat 6.
When a braking force is applied from the brake caliper 2 to the disk element 7 while the wheel 4 is in rotation, the disk element 7 generates a considerable amount of heat by frictional contact with the brake caliper 2. At this time, cooling air 12 flows through the cooling passage 11 between the first and second annular circular plates 8, 9, causing the cooling fins 10 to cool the disk element 7. The ventilated disk 1 is disposed in the wheel 4. Therefore, while an inner sliding surface 8a of the first annular circular plate 8 is cooled by cooling air 13, an outer slide surface 9a of the second annular circular plate 9 is not exposed to much cooling air, and cannot sufficiently be cooled.
Solid disk brake systems also suffer the same problem as with the ventilated disk 1.